As described in JP 2003-142041 A, an exemplary lead-acid battery includes a container and a lid member that is thermally welded to the container so as to seal the container. The lid member is thermally welded to the container in the following manner. Facing portions of the container and the lid member are initially heated using a heated iron plate. The lid member is subsequently placed on the container so that the facing portions thus heated abut against each other, and the container and the lid member are then pressed against each other. The facing portions of the container and the lid member are thus coupled together, and the lid member is thermally welded, for example, so as to be joined to the container.